You might have to wait for pg_is_in_recovery to be false after the promotion. (in 9.6 pg_ctl promote doesn't wait for promotion to complete unlike 10). [1]
You should CHECKOINT between 2 and 3. (or wait for the first checkpoint to finish) In the thread [2], Michael Paquier explains that:
" This makes the promoted standby update its timeline number in the on-disk control file, which is used by pg_rewind to check if a rewind needs to happen or not. "
